The invention relates to polyisocyanurate systems, fiber reinforced polyisocyanurate matrix composites, and manufacture of those composites by pultrusion.
Pultrusion is a highly cost effective method for making fiber reinforced, resin matrix composites. The primary raw materials used in pultrusion are resin and reinforcement. Fillers and additives such as calcium carbonate, clay, mica, pigments, UV stabilizers can be added to the resin to enhance the physical, chemical and mechanical properties of the pultruded product.
Pultrusion is typically done by the injection die or open bath process. The open bath process is the most common. The injection die process, however, is gaining importance due to environmental concerns about the large amounts of volatile contaminants released in the open bath process.
In a typical open bath process, reinforcement material in the form of fibers, mat or roving is pulled continuously through an open bath of resin to produce an impregnated reinforcement. The impregnated reinforcement is pulled through form plates to remove excess resin, and then through a curing die to cure the resin and yield a finished product.
In the injection die pultrusion process, reinforcement material is passed through a closed injection die that has resin injection ports. The resin is injected under pressure through the ports to impregnate the reinforcement material. The impregnated reinforcement is pulled through the injection die to produce a shaped product.
Resins which have been used in the open bath and injection die methods of pultrusion include thermoset resins such as unsaturated polyester, epoxy, phenolics, methacrylates and the like, as well as thermoplastic resins such as PPS, ABS, Nylon 6. Blocked polyurethane prepolymers also have been used. Polyester and epoxy resins are generally slower reacting than polyisocyanurates. In addition, the use of blocked polyurethane resins in pultrusion has the disadvantage of deblocking of the isocyanate which creates environmental concerns.
A need therefore exists for resins such as polyisocyanurate and polyurethane resins which may be used in pultrusion, especially injection die pultrusion, without these disadvantages.
The invention relates to polyisocyanurate systems, preferably miscible polyisocyanurate systems, having an isocyanate component and a polyol component. The polyol component includes any of polyester polyols and polyether polyols. One or more polyester polyols may be blended with one or more polyether polyols in any ratio for use in the polyol component.
The polyether polyols have a functionality of about 2 to about 6 and a molecular weight of about 300-6000. The polyol component also includes a catalyst capable of initiating both a urethane and an isocyanurate reaction. The isocyanate can be an isocyanate prepolymer. The isocyanate and the polyol component can be present in a ratio of about 0.3 to about 9.0 in an amount sufficient to yield an index of about 200 to about 900.
The polyol component also can include a chain extender such as glycerols and diols having at least about 2 hydroxyl groups and a molecular weight less than about 300. When a chain extender is present, the polyol may be present in an amount of up to about 1-99% and the chain extender may be may be present in an amount of up to about 1-99% based on total weight of the polyol component.
A preferred polyisocyanurate system includes an isocyanate component and a polyether polyol component where the polyether polyol is polyethylene oxide capped polypropylene oxide polyether polyol having ethylene oxide content of about 21%, a functionality of 2, and a hydroxyl value of 30 mg KOH/gm, the chain extender is dipropylene glycol, and the isocyanate is a mixture of 2,4xe2x80x2 MDI,4,4xe2x80x2 MDI and pMDI having about 19.5% 2,4xe2x80x2-MDI, 60.9% 4,4xe2x80x2-MDI, about 19.6% p-MDI, and an NCO value of 32.5. The polyisocyanurate systems, at an index of from about 300 to about 700 fully cure at 120-140 C. with an isocyanate conversion of about 90%. Another preferred polyisocyanurate system includes an isocyanate component and a polyether polyol component where the polyether polyol is PPG425 and the isocyanate is a mixture of 2,4xe2x80x2 MDI,4,4xe2x80x2 MDI and pMDI having about 19.5% 2,4xe2x80x2-MDI, 60.9% 4,4xe2x80x2-MDI, about 19.6% p-MDI, and an NCO value of 32.5.
The invention also relates to a pultrusion process for preparing a cured polyisocyanurate fiber reinforced polymer composite. The process entails pulling continuous fibers through an impregnation die, supplying a polyol component having a catalyst capable of initiating both a urethane reaction and a isocyanurate reaction, and an isocyanate component to a static mixer to produce a polyisocyanurate reaction mixture and feeding the reaction mixture to the impregnation die, contacting the fibers with the precursor mixture in the impregnation chamber for a time period and at a temperature sufficient to cause substantial polymerization of the reaction mixture within the impregnation chamber to produce a composite of fibers coated by the polyisocyanurate reaction mixture, directing the composite of coated fibers through a heated curing die to at least partially cure the polyisocyanurate reaction mixture to produce a solid fiber reinforced polyisocyanurate matrix composite, and drawing the cured composite from the die. The temperature in the impregnation chamber is less than the temperature required to initiate a polyisocyanurate reaction. The fibers are at ambient temperature before they enter the impregnation die. The fibers and the reaction mixture are supplied concurrently to the impregnation die. During pultrusion, the polyisocyanurate reaction mixture may be present in the injection die for less than about 50 seconds.
The polyisocyanurate systems of the invention are two component systems. Mixing of the two components can be achieved by using a static or dynamic mixer. A static mixer is preferred. Type I and Type II miscible two component polyisocyanurate systems are preferred.
Having summarized the invention, the invention will now be described in detail by reference to the following disclosure and non-limiting examples.
Glossary
The following names and abbreviations are understood to have the meanings defined below:
1. 1,4 BD is 1,4 butane diol;
2. 1,3 BD is 1,3 butane diol;
3. 2,3 BD is 2,3 butane diol;
4. 1,2 PD is 1,2 propane diol;
5. 2m 1,3 PD is 2-methyl-1,3-propane diol;
6. BiCat 8 is Bismuth-Zinc Neodeconate from Shepherd Chemical Co.;
7. Dabco DC 1027 is 30% triethylenediamine (TEDA) in Ethylene. Dabco 33LV is TEDA in DPG from Air Products and Chemicals, Allentown, Pa.
8. Dabco K15 is a catalyst of a potassium salt in a glycol from Air Products and Chemicals, Allentown, Pa.;
9. Dabco T-12 is 100% dibutyl tin dilaurate from Air Products and Chemicals, Allentown, Pa.;
10. Dabco T-45 is a potassium carboxylate catalyst from Air Products and Chemicals, Allentown, Pa.;
11. Dabco TMR is a tetra alkylammonium 2-ethylhexonate dissolved in DPG, from Air Products.;
12. Fomrez UL-29 is a mixture of octylmercapto acetate in a polyol carrier available from Witco Corporation, Greenwich, Conn.;
13. DEG is diethylene glycol;
14. DPG is dipropylene glycol;
15. Glycerin is 99.5% pure trihydroxy alcohol from Quaker Chemical Co.;
16. Isocyanate A is polymeric MDI having an MDI content of about 44 wt. % and an NCO value of about 30.7 from Huntsman Polyurethanes;
17. Isocyanate B is uretonimine modified 4,4xe2x80x2 MDI having an NCO value of 29 from Huntsman Polyurethanes;
18. Isocyanate C is a mixture of 2,4xe2x80x2 MDI,4,4MDI and pMDI having about 9.4% 2,4xe2x80x2-MDI, 60.9% 4,4xe2x80x2-MDI, about 29.7% p-MDI, and an NCO value of 32.1 from Huntsman Polyurethanes.
19. Isocyanate D is a mixture of 2,4xe2x80x2 MDI,4,4xe2x80x2 MDI and pMDI having about 19.5% 2,4xe2x80x2-MDI, 60.9% 4,4xe2x80x2-MDI, about 19.6% p-MDI, and an NCO value of 32.5 from Huntsman Polyurethanes.
20. Isocyanate E is a softblock MDI prepolymer formed from an EO capped polyoxypropylene diol having a molecular weight of 3740 and EO cap level of 27.1%, remainder polypropylene oxide, and which is 39.7 wt. % of the total prepolymer, 6% of the total prepolymer is a uretonimine carbodiimide modified pure 4,4xe2x80x2 MDI having an NCO content of 29.3%, and the remainder of the prepolymer is a mixture of 4,4xe2x80x2 and 2,4xe2x80x2 MDI in which the 2,4 MDI is about 2.2-2.8% of the mixed isomer stream, the softblock prepolymer having an NCO of 18.9-19.3 and a viscosity at 25 C. of 300-375 cps from Huntsman Polyurethanes.
21. Kemester 5721 from Witco Corporation, Greenwich, Conn. is tridecyl stearate.
22. LC-5615 is nickel acetylacetonate from OSI Specialties;
23. LHT 240 is a polyether polyol from Arco Chemical Co.
24. Loxiol G71S is the reaction product of adipic acid, pentaerythritol, and oleic acid, having an acid number less than 15 and an hydroxyl number less than 15 from Henkel Corp., Kankakee, Ill.;
25. LuWax OP is a solid montanic ester wax from BASF Corp.
26. MDI is diphenylmethane diisocyanate;
27. MEG is monoethylene glycol;
28. Munch 7027/A is a fatty acid ester derivative internal mold release agent from Munch Co, Germany;
29. Munch 7016 is a fatty acid ester derivative internal mold release agent from Munch Co, Germany;
30. Munch 0669/1BB is a fatty acid ester derivative internal mold release agent from Munch Co, Germany;
31. Niax L 5440 is a silicone surfactant that includes polyalkylenoxidimethyl siloxane copolymer available from Union Carbide, Sisterville, W.Va.
32. Polymeric MDI is defined as a blend of 2,2xe2x80x2 MDI, 2,4xe2x80x2 MDI, and 4,4xe2x80x2 MDI diisocyanates, where 4,4xe2x80x2 MDI is the predominate isomer, the remainder being isocyanates having a functionality greater than 3. The weight ratio of diisocyanates to higher functionality isocyanates varies from 70:30 to 30:70.
33. Polyol A is polyethylene oxide capped polypropylene oxide polyether polyol having ethylene oxide content of about 21%, a functionality of 2, and a hydroxyl value of 30 mg KOH/gm from Huntsman Polyurethanes;
34. Polyol B is polyethylene oxide capped polypropylene oxide polyether polyol having ethylene oxide content of about 27%, a functionality of 2, and a hydroxyl value of 30 mg KOH/gm from Huntsman Polyurethanes;
35. Polyol C is polyethylene oxide capped polypropylene oxide polyether polyol having ethylene oxide content of about 50%, a functionality of 2, and a hydroxyl value of 30 mg KOH/gm from Huntsman Polyurethanes;
36. Polyol D is a glycerol based polyethylene oxide capped polypropylene oxide polyether polyol having an ethylene oxide content of about 10%, a functionality of 3, and a hydroxyl value of 56 mg KOH/gm from Huntsman Polyurethanes;
37. Polyol E is a glycerol based polyethylene oxide capped polypropylene oxide polyether polyol having an ethylene oxide content of about 17%, a functionality of 3, and a hydroxyl value of 35 mg KOH/gm from Huntsman Polyurethanes;
38. Polyol F is a glycerol based polypropylene oxide polyether polyol having a functionality of 3 and a hydroxyl value of 28 mg KOH/gm from Huntsman Polyurethanes;
39. Polyol G from Huntsman Polyurethanes is an ethylene glycol/diethylene glycol initiated adipate polyester polyol having an average molecular weight (g/mol) of 2000, a functionality of 2.0, and a hydroxyl number of 55 mg KOH/gm.
40. Polyol H from Huntsman Polyurethanes is an ethylene glycol/butane diol initiated adipate polyester polyol having an average molecular weight (g/mol) of 2000, a functionality of 2.0, and a hydroxyl number of 55 mg KOH/gm.
41. Polyol X from Huntsman Polyurethanes has an average molecular weight (g/mole) of 260. Polyol X is a polyether diol that has a functionality of 3 and a hydroxyl number of 650 mg KOH/g. Polyol X is all PO tipped.
42. Polyol Y is a polyether polyol made by propoxylated glycerol and typically with 7% ethylene oxide. It has a hydroxyl value of 55 mg KOH/gm and is ethylene oxide tipped triol;
43. Polycat 46 is 38% potassium acetate in ethylene glycol(hydroxyl values 68.7), a strong trimer catalyst from Air Products and Chemicals, Allentown, Pa.;
44. PPG is polypropylene glycol;
45. PPG 200 is propylene glycol having a molecular weight of 200 from ARCO Chemical;
46. PPG 425 is propylene glycol having a molecular weight of 425 from ARCO Chemical;
47. PPG 1000 is propylene glycol having a molecular weight of 1000 from ARCO Chemical;
48. PPG 2000 is propylene glycol having a molecular weight of 2000 from ARCO Chemical;
49. Rucoflex S-2011-35 is a polyester polyol from Ruco Corporation, Hicksville, N.Y. having a molecular weight of 3000, a OH value of 35 and a functionality of 2.0
50. Rucoflex S-2011-35 is a polyester polyol from Ruco Corporation, Hicksville, N.Y. having a molecular weight of 2000, a OH value of 55 and a functionality of 2.0
51. Rucoflex S-2011-35 is a polyester polyol from Ruco Corporation, Hicksville, N.Y. having a molecular weight of 1000, a OH value of 110 and a functionality of 2.0
52. Stepanpol SP-1752 from Stepan Corporation, Northfield, Ill. 60093, is a diethylene glycol/orthophthalate polyester polyol having an average molecular weight (g/mol) of 640, a functionality of 2.0, and a hydroxyl value of 640 mg KOH/gm
53. TEG is triethylene glycol;
54. UAX 1075 is a blocked amine catalyst from OSI Specialties;
55. Unitol DSR from Unichem, Chicago, Ill. is a fatty acid derivative of oleic acid and linoleic acid.
56. Wurtz INT 6871 is an internal mold release agent for polyurethane foams from Wurtz, Bingen-Sponsheim, Germany;
57. Wurtz PAT 672 is an internal mold release agent for polyurethane rigid foams from Wurtz, Bingen-Sponsheim, Germany;
58. Molecular weight is number average.
Polyisocyanurate Systems
The isocyanates employed in the polyisocyanurate systems of the invention typically have viscosities of from about 50 to about 1500 centipoise(xe2x80x9ccpsxe2x80x9d), preferably about 50 to about 400 cps.
Isocyanate prepolymers may also be employed in the polyisocyanurate systems of the invention. Useful prepolymers which may be employed have a NCO value of from about 9 to about 26, preferably about 10 to about 26. Useful isocyanate prepolymers may be based on any of toluene diisocyanate, naphthalene diisocyante, hexamethylene diisocyante, MDI, hydrogenated MDI, and tetramethylxylene diisocyante.
The polyols employed in the polyisocyanurate systems of the invention typically have a viscosity of about 200 to about 8500 cps, preferably about 400 cps to about 1000 cps.
Useful polyols include polyether polyols and polyester polyols. Polyether polyols include those prepared by reacting alkylene oxides, aromatic-substituted alkylene oxides or mixtures thereof with an active hydrogen-containing initiator compound. Suitable oxides include ethylene oxide, propylene oxide, 1,2-butylene oxide, styrene oxide, epichlorohydrin, epibromohydrin, and mixtures thereof. Suitable initiator compounds include water, ethylene glycol, propylene glycol, butanediol, hexanediol, glycerine, trimethylol propane, pentaerythritol, hexanetriol, sorbitol, sucrose, hydroquinone, resorcinol, catechol, bisphenols, novolac resins, phosphoric acid and mixtures thereof. Other suitable initiators further include, for example, ammonia, ethylenediamine, diaminopropanes, diaminobutanes, diaminopentanes, diaminohexanes, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentamethylenehexamine, ethanolamine, aminoethylethanolamine, aniline, 2,4-toluenediamine, 2,6-toluenediamine, 2,4xe2x80x2-diaminodiphenylmethane, 4,4xe2x80x2-diaminodiphenylmethane, 1,3-phenylenediamine, 1,4-phenylenediamine, naphthylene-1,5-diamine, triphenylmethane 4,4xe2x80x2,4xe2x80x3-triamine, 4,4xe2x80x2-di(methylamino)diphenylmethane, 1,3-diethyl-2,4-diaminobenzene, 2,4-diaminomesitylene, 1-methyl-3,5-diethyl-2,4-diaminobenzene, 1-methyl-3,5-diethyl-2,6-diaminobenzene, 1,3,5-triethyl-2,6-diaminobenzene, 3,5,3xe2x80x2,5xe2x80x2-tetra-ethyl-4,4xe2x80x2-diamino-diphenylmethane, and amine aldehyde condensation products such as the polyphenylpolymethylene polyamines produced from aniline and formaldehyde and mixtures thereof.
Useful polyester polyols which may be employed include those prepared by reacting a polycarboxylic acid or anhydride with a polyhydric alcohol. The polycarboxylic acids may be aliphatic, cycloaliphatic, aromatic and/or heterocyclic and may be substituted (e.g., with halogen atoms) and/or unsaturated. Examples of suitable carboxylic acids and anhydrides include succinic acid; adipic acid; suberic acid; azelaic acid; sebacic acid; phthalic acid; isophthalic acid; terephthalic acid; trimellitic acid; phthalic acid anhydride; tetrahydrophthalic acid anhydride; hexahydrophthalic acid anhydride; tetrachlorophthalic acid anhydride; endomethylene tetrahydrophtalic acid anhydride; glutaric acid anhydride; maleic acid; maleic acid anhydride; fumaric acid; dimeric and trimeric fatty acids, such as those of oleic acid, which may be in admixture with monomeric fatty acids. Simple esters of polycarboxylic acids may also be used as starting materials for polyester polyols, such as terephthalic acid dimethyl ester, terephthalic acid bisglycol ester and mixtures thereof.
Useful weight ratios of isocyanate to polyol in the polyisocyanurate systems of the invention vary from about 0.3 to about 9.0, preferably about 0.6 to about 6.0, more preferably about 0.8 to about 1.2.
In order to cure the polyisocyanurate systems during pultrusion and to obtain good conversion to polyisocyanurate, a catalyst capable of initiating both a urethane and an isocyanurate reaction is included in the polyol component. Advantageously, catalysts in very small amounts of less than about one percent by weight based on the total weight of the polyol component may be used. Useful catalysts include tin salts such as stannous octoate and dibutyl tin dilaurate, tertiary amines such as diaminobicyclooctane, N,N dimethylcyclohexyl amine, N-methylmorphine, and N-methylimidazole, alkali carboxylates such as potassium 2-ethylhexanoate, potassium tetraalkylammonium carboxylates, sodium 2-ethylhexanoate, and sodium tetraalkylammonium carboxylate, and alkaline earth carboxylates such as strontium 2-ethylhexanoate and strontium tetraalkylammonium carboxylate. Alkali carboxylates are preferred.
Type I Polyisocyanurate Systems
Type I polyisocyanurate systems which include a polyol component having a chain extender and a catalyst, and an isocyanate component are formulated by blending. In Type I systems, the polyol may be present in an amount of up to about 1-99% and the chain extender may be present in an amount of up to about 1-99% based on total weight of the polyol component.
The polyols used in Type I polyisocyanurate systems typically have a molecular weight of about 300-6000, preferably about 1000 to about 6000 and a functionality of about 2 to about 4. More preferably, the polyols have a functionality of about 2 to about 3 and a molecular weight of about 2000 to 6000.
Polyols employed in Type I polyisocyanurate systems typically are polyethylene oxide capped polypropylene oxide polyether polyols having about 10 wt. % to about 50 wt. % ethylene oxide, a functionality of about 2, and a hydroxyl value of about 30 mg KOH/gm. These polyols are well known in the art and are commercially available. Examples of these polyols include Polyol A, Polyol B, Polyol C, Polyol D, Polyol E and Polyol F as defined above. Polyols such as Polyols A-F can be made by the addition of alkylene oxides such as ethylene and propylene oxide onto alcohols and amines which serve as initiators. Examples of these initiators include glycerol, DPG, and MEG.
Chain extenders which can be used in Type I polyisocyanurate systems include glycerols and diols which have at least 2 hydroxyl groups and a MW less than about 300. Useful chain extenders include glycerols and diols which have primary hydroxyl groups, glycerols and diols which have secondary hydroxyl groups and glycerols and diols which have both primary and secondary hydroxyl groups. Preferably, the chain extenders are glycerols and diols which have secondary hydroxyl groups and a molecular weight of more than about 62. Examples of these chain extenders include but are not limited to DEG, TEG, 2,3 BD, 1,2 PD, and DPG, preferably 1,2 PD and DPG.
Various additives may be included in the polyol component employed in Type I and Type II polyisocyanurate systems to control shrinking, color, mechanical properties, and fire retardance and release properties. Useful release agents include but are not limited to fatty amides such as erucamide or stearamide, fatty acids such as oleic acid, -amino oleic acid, fatty esters such as Loxiol G71S, carnuba wax, beeswax (natural esters), butyl stearate, octyl stearate, ethylene glycol monostearate, ethylene glycol distearate and glycerine monooleate, and esters of polycarboxylic acids with long chain aliphatic monovalent alcohols such as dioctal sebacate, mixtures of (a) mixed esters of aliphatic polyols, dicarboxylic acids and long-chained aliphatic monocarboxylic acids, and (b) esters of the groups: (1) esters of dicarboxylic acids and long-chained aliphatic monofunctional alcohols, (2) esters of long-chained aliphatic monofunctional alcohols and long-chained aliphatic monofunctional carboxylic acids, (3) complete or partial esters of aliphatic polyols and long-chained aliphatic monocarboxylic acids, in a tratio of (a) to (b) of from 1:3 to 9:1; silicones such as Tegostab L1-421T, Kemester 5721, metal carboxylates such as zinc stearate and calcium stearate, waxes such as montan wax and chlorinated waxes, fluorine containing compounds such as polytetrafluoroethylene, phosphates and chlorinated phosphates.
Useful additives for control of mechanical properties include calcium carbonate, barium sulfate, clay, aluminum trihydrate, antimony oxide, milled glass fibers, wollastonite, talc, mica, etc. These additives can be included in and added to the polyol component in amounts of up to about 65% based on the total weight of the polyol component.
In Type I polyisocyanurate systems, the isocyanate component may be any of 2,4xe2x80x2 MDI, 4,4xe2x80x2 MDI, polymeric MDI, blocked isocyanate, and ternary blends thereof. Examples of useful isocyanates include isocyanates A-D as defined above. Typically, ternary isocyanate blends such as isocyanate C and isocyanate D are prepared by mixing a standard polymeric MDI with a blend of 2,4xe2x80x2 MDI and 4,4xe2x80x2 MDI. Standard polymeric MDI is a mixture of functionality 2 and higher species such that the average functionality is about 2.5 to 2.8. See (G. Woods., The ICI Polyurethanes Book, sec. ed. John Wiley, N.Y. 1990, page 34-35).
In Type I polyisocyanurate systems, the polyol, chain extender and isocyanate may be varied to control the miscibility of the reaction mixture formed. Generally, for an isocyanate having a given 2,4xe2x80x2-MDI content, the miscibility of the polyol component-isocyanate reaction mixture may be increased by using polyols which have higher amounts of ethylene oxide (xe2x80x9cEOxe2x80x9d)content. Polyols with higher ethylene oxide contents up to about 50% ethylene oxide content are preferred. Chain extenders which have higher levels of secondary hydroxyls also may be used to increase the miscibility of the reaction mixture. Chain extenders which have secondary hydroxyls and a molecular weight greater than 62 are preferred. Isocyanates with higher amounts of 2,4xe2x80x2-MDI are preferred to achieve increased miscibility.
Type II Polyisocyanurate Systems
In Type II polyisocyanurate systems, the isocyanate component may be any of 2,4xe2x80x2 MDI, 4,4xe2x80x2 MDI, polymeric MDI, and blends thereof. Examples of useful isocyanates include isocyanates A-D as defined above. Typically, ternary isocyanate blends such as isocyanate C and isocyanate D are prepared by mixing a standard polymeric MDI with a blend of 2,4xe2x80x2 MDI and 4,4xe2x80x2 MDI.
Type II polyisocyanurate systems employ polyether polyols which have an EO content less than about 15 wt. % and a molecular weight of about 300-2000, preferably about 300-1000. The functionality of the low EO polyether polyols employed is about 2 to about 6, preferably about 2 to about 3, most preferably about 2. Examples of useful low EO polyether polyols include PPG 425, Polyol F, PPG 1000, PPG 2000 and Polyol D. Blends of low EO polyether polyols also can be used as the polyol component. In this aspect, the MW of the individual polyether polyols is about 175 to about 1000.
Pultrusion of Type I and Type II Polyisocyanurate Systems
Type I and Type II polyisocyanurate systems, preferably Type I systems, may be used to produce pultruded neat polyisocyanurates as well as pultruded polyisocyanurate composites.
Polyisocyanurate systems of the invention having indices of from about 200 to about 1000, preferably about 300 to about 600 may be pultruded. Polyisocyanurate systems which include fire retardant additives may be pultruded at indices of about 300 to about 900.
The reaction mixtures formed from the polyisocyanurate systems employed in the invention have numerous advantages for use in pultrusion. These advantages include long pot life at ambient temperatures, ability to be easily mixed, viscosities suitable for good wet-out of the reinforcement material under resin injection conditions, good bonding with the reinforcement material even when unsized, and snap-cure characteristics when heated to a specific temperature. For example, Type I and Type II polyisocyanurate systems at an index of from about 300 to about 900 are fully cured at about 120-140xc2x0 C. in about 1 minute with an isocyanate conversion of about 95%. The polyisocyanurate systems employed in the invention can be pultruded in the presence of glass fiber reinforcement to produce glass fiber reinforced, polyisocyanurate composites and cured in-situ at elevated temperatures.
Miscibility Evaluation
In order to evaluate the miscibility of the polyisocyanurate systems employed in the invention, one gram of isocyanate is placed on a watch glass. Then, the polyol component is added to achieve an index of 650. The polyol component and the isocyanate are mixed by hand with a spatula for 30 seconds. The resulting reaction mixture is evaluated for clarity. If the reaction mixture is clear within 30 seconds after mixing is stopped, then the polyisocyanurate system is considered miscible.
The invention will now be further illustrated by reference to the following non-limiting examples.
Type I Immiscible Polyisocyanurate Systems